If someone had told New York Yankees manager Joe Girardi in February that his recently reinforced rotation would be eagerly anticipating a boost from lefthander Andy Pettitte, he either would have laughed out loud or offered a confused glare similar to the one of the Aflac duck in that old Yogi Berra commercial.

But that is precisely how things have evolved in the Bronx, where Pettitte will make his 2012 debut Sunday against the Seattle Mariners.

Before pitchers and catchers officially reported to spring training, longtime Yankees catcher/DH Jorge Posada joined Pettitte in retirement, leaving shortstop Derek Jeter and closer Mariano Rivera as the only active members of the franchise’s legendary Core Four. Well, Rivera has been lost for the season because of a fluky knee injury and Pettitte is approaching his first major league start since Game 3 of the 2010 ALCS.

Perhaps even more unlikely than that turn of events is the fact that the Yankees suddenly are counting on Pettitte to rescue a rotation that has been plagued by injury and inconsistency.

“If there’s a gap between the old Andy Pettitte and what we’re going to get, I don’t know yet,” Yankees general manager Cashman told reporters. “It’ll be nice to get another healthy arm in the mix.”

Following a flurry of moves in January, the question was how New York would handle its surplus of starting pitchers. These days, the more pertinent question is whether the team can withstand its deficiency of quality starters.

Righthander Michael Pineda, the 23-year-old flame-thrower acquired from the Seattle Mariners, was lost for the season before the season even began because of a shoulder injury that required surgery. Veteran righthander Freddy Garcia, who revitalized his career with the Yankees in 2011, pitched so poorly in April that he was moved to the bullpen in favor of rookie David Phelps. Righthanders Phil Hughes (6.67 ERA) and Ivan Nova (5.02 ERA) have vastly unperformed, and even ace lefthander CC Sabathia hasn’t exactly lived up to his 4-0 record.

With a 3.75 ERA, free-agent pickup Hiroki Kuroda has been the team’s most consistent starter—and he has pitched six innings in just three of his six starts.

New York’s rotation ranks 26th in the majors with a 5.41 ERA and 27th in batting average allowed (.290), it has allowed the second-highest homer total (29) and it is without a complete game.

So, yes, Pettitte suddenly is more of a savior than a sideshow.

What remains to be seen, of course, is how much Pettitte has left. He posted a very respectable 3.28 ERA in 2010, but he was limited to 21 starts because of injuries. After more than a year on the sidelines, his durability is even more questionable.

And then there is his minor league performance. Pettitte posted a 3.71 ERA during his four rehab starts, but he has a 5.40 ERA and 1.80 WHIP in his two starts above the Class A level.

But this is Andy Pettitte, a 240-game winner and the majors’ all-time leader in postseason wins. He wouldn’t have decided to return—and wouldn’t have opted to continue his comeback attempt—if he didn’t feel as if he still could compete on a high level.

Sabathia still is the ace, Kuroda still is a solid No. 2 and a strong case can be made that Nova will regain his 2011 form. So, while much will be asked of him, it isn’t as if the fate of the Yankees’ 2012 season is riding on Pettitte’s 39-year-old left arm.